It is well established that ion implantation can alter the electrical, mechanical, and optical properties of a material. For example, the surface conductivity, surface hardness and refractive index of a substrate, such as for example a crystalline insulator, can be altered or otherwise modified through ion implantation, such as for example ion implantation-induced amorphization. More complex alterations in the optical response of ceramic materials, such as for example insulators, are also possible with ion implantation and involve altering or otherwise affecting the susceptibility and dielectric constant of the material through the formation of a dilute concentration of colloidal particles. It has been demonstrated that particles on the order of 10 nm and smaller dispersed in a dielectric medium exhibit novel optical properties by a wide range of researchers, including White, et al., Mat. Res. Soc. Symp. Proc., 316, 499 (1994); Mouritz, et al., Nuc. Inst. & Meth. B, B19/20, 805 (1987); Haglund Jr., et al., Nuc. Inst. & Meth. B, B91, 493 (1994); and Allegre, et al., J. Cryst. Growth., 138, 998 (1994), incorporated herein by reference. The small size of these particles induces electronic conditions in the material which cause the material to respond in a nonlinear fashion in response to applied electromagnetic fields. These nonlinear responses are essential for the formation of many planar waveguide devices required for integrated optical device technology, such as integrated optical computing, high band-width optical switching and in other areas concerned with unconventional optical responses.
Colloid formation in many materials can be induced by any mechanism that causes the introduction of a significant amount of free metal ions. Townsend, Rep. Prog. Phys., 50, 501 (1987). Ion implantation is clearly such a mechanism and particle formation via ion implantation has been demonstrated in MgO, CaO, SrO, SiO.sub.2 and Al.sub.2 O.sub.3. This type of particle formation involves the creation of a supersaturated region in the substrate material by ion implantation and the subsequent precipitation of the extra metal to form metallic particles. For example, ion implantation of Al.sub.2 O.sub.3 with any one of a large range of ions results in the formation of particles composed of that element embedded in the substrate. Elements for which implantation induced particle formation in Al.sub.2 O.sub.3 has been demonstrated include Au, Ag, Cu, Fe, Ni, Mn, Si and Ge. Farlow, et al., Rep. Prog. Phys., 50, 501 (1987); Sklad, et al., J. Mat. Sci., 27, 5895 (1992); Ohkubo, et al., J. Appl. Phys., 60, 1325 (1986); White, et al., Mat. Res. Soc. Symp., 396, 377 (1996); Magruder, et al., Appl. Phys. Lett., 62, 465 (1993); Freire, et al., Mat. Res. Soc. Symp., 396, 385, (1996); and Haglund Jr, et al., Opt. Lett., 18, 373 (1993). Similarly, ion implantation of SiO.sub.2 with Si, Au, Ag, As, Cu, Fe, Ge, In, P, Sb, W or Zn result in particles composed of the respective implanted ion. White, et al., Mat. Res. Soc. Symp. Proc., 316, 499 (1994); Farlow, et al., J. Mat. Res. 5, 1502 (1990); Atwater, et al., Mat. Res. Soc. Symp., 316, 409 (1994); Tyschenko, et al., Mat. Res. Soc. Symp., 438, 453 (1997); Pan, et al., Nucl. Instrum. & Meth. B, 114, 281 (1996); Magruder, et al., Mat. Res. Soc. Symp., 438, 429 (1997); Hosono, et al., Nucl. Instrum. & Meth. B, 116, 178 (1996); Battaglin, et al., Nucl. Instrum. & Meth. B, 116, 102 (1996); Kishimoto, et al., Mat. Res. Soc. Symp., 438, 435 (1997); Perez, et al., J. Mat. Sci., 2, 91, (1987); Min, et al., Mat. Res. Soc. Symp., 405, 247 (1996); Bao, et al., Mat. Res. Soc. Symp., 438, 477 (1997); Anderson, et al., J. NonCryst. Solids, 203, 114 (1996); Mu, et al., Mat. Res. Soc. Symp., 438, 441 (1997).
This method of particle formation does have drawbacks, however. While ion implantation does allow a wider range of material combinations than traditional melt processing, there are certain combinations that have not been demonstrated using this method. Aluminum particles in Al.sub.2 O.sub.3, for example, have not been shown to occur upon implantation of Al. Another deficiency of this method is that the particle size distribution of particles formed via implantation and precipitation can be quite large. Size ranges up to approximately 35 nm have been reported in some cases. Sklad, et al., J. Mat. Sci., 27, 5895 (1992). Many of the applications mentioned above require a narrower particle size distribution in order to allow for more precise control of the induced optical properties. Atwater, et al., Mat. Res. Soc. Symp., 316, 409 (1994); Tyschenko, et al., Mat. Res. Soc. Symp., 438, 453 (1997). In addition, the nature of the precipitation mechanism requires that the particles formed be the equilibrium crystallographic phase of the metal. In some cases other phases may be desired, as the electrical properties of a material can be different depending on the crystallographic structure.
Particle formation via implantation and reduction addresses these problems. It allows for the formation of certain substrate-particle systems not demonstrated with other particle formation techniques, and can produce a narrower particle size distribution. Hunt, et al., Proc. Microscopy and Microanalysis, 534 (1996); Hunt, et al., J. Mat. Sci., 32, 3393 (1997); Hunt, et al., Proc. Microscopy and Microanalysis, 413 (1997). In addition, it has been demonstrated that particles with a nonequilibrium structure can be produced with this technique.